Demolition tool with shock attenuating means



April 20, 1965 M. ox-'ARRELL DEMOLITION TOOL WITH SHOCK ATTENUATINGMEANS Filed June 14, 1962 2 Sheets-Sheet 1 /f F/G. 3

FIG. 2

United States Patent Leu 3,17,185 DEMULITIN TOUL WlTH SHCK ATTENUATNGMEANS Matthew GFarrell, Utica, NY., assigner to` Chicago Pneumatic ToolCompany, New York, NEI., a corporation of New .lersey Filed June 14,1962, Ser. No. 202,606

3 Claims. (Cl. 173-133) This invention is concerned with improvements inpercussive tools, particularly manually portable tools commonly known aspavement breakers or ldemolition tools.

Such tools include a hammer piston which is pneumatically reciprocatedto repeatedly pound an anvil against a work steel, the work steel havinga tapered work end or peg point used for breaking up the work. At times,the work steel becomes so tightly embedded in the work as to make itextremely difficult for the operator to withdraw it. lt is commonpractice when this occurs for the operator to pull the entire toolslidably backward relative to the work steel, and then to operate thetool so as to jar the stuck steel loose. Often the result of such actionin tools of conventional structure is damage of the tool, such as acracked front head or breakage of associated parts. This is because thepowerful impacting force of the piston that would ordinarily betransmitted through the anvil to the work steel is instead transmittedto the casing of the front head. At other times, the work steel will runout, as when it suddenly breaks through the work into soft earth or intoa vacant area. Continued operation of the tool following such action isalso likely to result in damage to the front head and associated parts,

since in this case the impacting force of the piston will also betransmitted to the casing of the front head instead of to the Worksteel.

An object of this invention is to improve such tools so as to avoid thelikelihood of damage occurring to the tool when the tool is operated toloosen stuck steel, or when the steel has run through the work.

A further object of this invention is to provide in such tools means forchecking or attenuating the impacting force of the piston relative tothe anvil when the usual support provided by the work steel is removedfrom the anvil.

A still further object of this invention is to improve these tools insuch manner that when the support of the work steel is removed from theanvil, the impacting force of the piston against the anvil will be soattenuated as to eliminate the likelihood of the tool being damaged, butsuilicient residual force will nevertheless be transmitted to the casingof the front head to jar a stuck steel loose when the tool is operatedfor the latter purpose.

The invention further lies in the particular construction andarrangement of its component parts, and also in their particularcooperative association with one another to effect the objects intendedherein.

The foregoing and other objects and advantages of this invention willappear more fully hereinafter from a consideration of the detaileddescription which follows, taken together with the accompanyingdrawings, wherein an embodiment of the invention is illustrated. It isto be expressly understood, however, that the drawings are for purposesof illustration and description; and they are not to be construed asdening the limits of the invention.

In the drawings:

FlG. 1 is a longitudinal section through a manually portable percussivetool embodying the invention; and it shows the tool in its normaloperating condition with the peg point of the work steel pressed againstthe solid work or pavement;

FIG. 2 is a plan view of the elastic unit;

HG. 3 is a longitudinal section through the elastic unit;

Mice

FIG. 4 is a view to that of FIG. l', but shows the work steel stuck fastin the pavement, and further shows the anvil and work steel in their lowpositions relative to the casing;

FIG. 5 is a fragmentary View of the tool showing the work steel ashaving run through the pavement; and

FIG. 6 is a sectional view showing what takes place when the piston isreciprocated relative to the anvil in the condition of the tool shown inFIG. 4, or FIG. 5.

There is illustrated in the drawings various views of a pneumaticallypowered manually portable percussive tool 1li in which the invention`isembodied. The tool is of a conventional type commonly known as apavement breaker or demolition tool. The tool includes a housing orcasing 11 having a front head section 12 which is secured by the usualtie-bolts, not shown, to a piston cylinder 13. The usual back-head 9 isassociated with the upper end of the piston cylinder, and includes ahandle 8 for guiding the tool during its operation, or for lifting orcarrying it.

A hammer piston 1d is pneumatically reciprocable in the cylinder 13 topound an anvil l5 relative to the work steel i6. During normal operationof the tool, as will be later described, the piston is enabled, withoutinterference, to impart its full driving force against the anvil. Duringother times, as will also 'be later described, attenuating means iscaused to materially check the movement of th piston on its work strokebefore it is permitted to strike the anvil.

The attenuating means comprises a sleeve or slide member 18 and anelastic unit or elastometerl 19. The sleeve member 1S has axial movement(FIG. 6) between a hori- Zontal upper shoulder 21 and a coned lowershoulder 22 of the casing. The sleeve is supported by the elastic unit19 so that an upper flat shoulder 23 of the sleeve normally limitsagainst the corresponding shoulder 21 of the casing (as in FlG. 4). Theelastic unit 19 comprises (FIGS. 2 and 3) a pair of cylindrical metaltubes 24 and 25 of different diameters, arranged one within the other inparallel spaced relation and bonded to each other by means of a strongelastic material 2d filling the space between them. The elastic materialillustrated here is a strong plastic, commonly known as neoprene. Theouter tube 24 is seated in an annular recess 27 of the casing; and it isrestrained against relative axial movement by means of a pair of opposedannular shoulders 2d of the casing. The inner tube 25 sleeves about thecentral `area of the sleeve 1d, and its upper end abuts an overhangingshoulder 29 of the sleeve. The sleeve 18 has an upper coned centralsurface 31 which is adapted to be struck at certain times by acomplementary coned undersurtace 32 of the piston as the latterreciprocates. When this occurs, the sleeve 13 is forced or slid downwardagainst the yielding resistance of the elastic unit 19 to engage a conedbottom end 33 thereof against the annular shoulder 22 of the casing, asappears in FIG. 6. As the sleeve moves downward, it carries the innertube 25 of the elastic unit with it, causing the elastic element 26 toelastically deform downward. Such action of the piston against thesleeve will materially check or absorb the downward driving force of thepiston. When the sleeve 13 is relieved of the stress or impacting forceof the piston, as when the piston moves upwardly or away on its returnstroke, the sleeve is returned to normal position (FIG. 4 as the elasticelement` 26 naturally restores. The sheer strength of the elasticelement is so computed that it will have absorbed about half the energyimparted by the piston to the sleeve 18 when the latter is stopped bythe shoulder 22.

The anvil l5 has limited axial movement relative to the sleeve member18. The anvil is guided in thismovernent by means of an enlarged lowerbody portion 3d thereof which bears against the adjacent wall of thesleeve; and it is further guided by means of a reduced upper elongatedstem portion 35 which bears against a reduced inner annular surface 3dof the sleeve. The anvil has an elevated or normal operating position(FIG. l) in which a'coned shoulder 37 thereof limits against acomplementary shoulder 38 of the sleeve, and in which the stem 35projects in part out of and above the sleeve into the piston cylinder13. rfhe anvil has a low or relaxed position (FIG. 4) in which a conedundersurface 3% thereof seats upon a complementary shoulder il of thecasing; and in which a fiat top end d2 of the stem 35 is positioned ashort distance below the lowermost edge 43 of the coned upper surface 3lof the sleeve. The low position of the anvil relative to the -sleeve i8is such that the sleeve must rst be moved downwardly a little by theimpacting action of the piston, as appears in FIG. 6, before the tlatbottom end de of the piston can strike the opposed end v adapted toengage the work. The work is here illustrated as a concrete pavementdil. A tail portion it? of the work steel is axially slidable in astationary bushing 5l of the casing. A lange portion 52 of the worksteel has limited movement below the bushing in an enlarged area 53 ofthe casing. A lug or stop Se, carried by the casing and projectingradially into the path of movement of the flange 52B, not only preventsendwise escape of the Work steel from the front head of the tool, butalso cooperates with the rlange to determine the lowermost position ofthe work steel relative to the casing.

The work steel has an elevated position, as indicated in PEG. 1, duringnormal operation of the tool. in this situation the peg point 47 pressesagainst the solid pavement d8, so that the tail portion C@ of the worl;steel is elevated in the bushing 5l relative to the casing. ln itselevated position, the rear portion of the work steel projects axiallyout of the bushing beyond the annular shoulder il of the casing; and thefiat top end 553 of the worli steel presses upwardly against the bottomend 5d of the anvil to hold the anvil raised in its elevated pcsition.Thus, the top end 42 of the elevated anvil pro'ec into the pistoncylinder, and the coned undersurlace of the anvil is clear of the casingshoulder lll. Accordingly, as the piston i4 reciprocates, its fullimpacting force is imparted to the anvil l5 and transmitted through thelatter to the work steel. As the work steel digs intoV the pavement, thefront head l2 of the tool has equal downward relative movement, thusenabling the work steel to continuously hold .the anvil in its elevatedposition y during normal operation of the tool.

At times, the work steel will become so embedded in the work, as appearsin FlG. 4, that the operator is nuable to withdraw it. When this occurs,the operator pulls back on the handle S so as to slide or draw theentire toolby means of the bushing 51 rearwardly relative to the stuckwork steel until the flange 52 of the latter abuts against the stop lug54. When the operator does this, the tail end 55 of the work steel willhave a position in the bushing 5l as in FlG. 4, below the shoulder il ofthe casing and clear of the bottom end 56 of the anvil. The anvil, whichgravitationally follows the downward relative movement of the work steelas the casing is pulled back, will seat upon the shoulder lll of thecasing. The piston is then reciprocated or operated while the tool isthus held by the operator. As the piston reciprocates, its impactingforce will be largely checked by the attenuating means in the mannerearlier described. ln this operation of the tool a jarring action willbe imparted to the casing as the sleeve liti impinges on the shoulder 22and as the anvil receives the residual impacting force of the piston.This jarring action is insufficient to crac-li or otherwise damage thecasing of the tool, its front l?. or associated parts; but it functionsto cause the operator to recoil and transmit through the stop lug 5d andflange 52 to the work steel a sutlicient and necessary rearwardly actingforce to jar the latter loose from its stuck condition in the pavementfili.

At other times, the work steel will suddenly run through the work intosoft earth or into a vacant area below, as in FIG. 5. When this occurs,the entire tool by its own weight and under the pressing force beingexerted by the operator upon the handle follows the sudden droppingaction of the work steel until the bottom end 46 of the casing abuts thehard pavement. When this occurs, the anvil l5 and the work steel 1.6will have dropped to their low positions, 'which will be the san e asthat shown in FG. 4. No advantage is to be gained by operating the toolin this situation. But, the operator is not always able to immediatelystop the action or the reciprocating piston under these circumstances sothat the piston may continue to reciprocate for another cycle or sobefore he does stop it. However, the d ving force of the piston will belargely attenuated by attenuating means, as earlier described, and nodam ge will oscar to the casing or the associated parts of the toolshould such further cycling of the piston occur.

lt is to be appreciated that in either of the two situations mentioned,namely, when the work steel is stuck in the Work, and when the worlt`steel runs through the work; if the full force of the piston weredirected to the anvil while the latter is unsupported by the work steeland while the anvil rests upon the shoulder fil of the casing, thelatter and its associating parts would very likely be cracked orotherwise damaged. y

While an embodiment of the invention has been illustrated and describedin detail, it is to be expresny understood that the invention is notlimited thereto. Various changes might possibly be made in the designend arrangement of the parts without departing from the spirit and scopeof the invention. it is intended, therefore, to claim the invention notonly as shown and described, but also in all such forms andmodifications thereof as may be reasonably construed to fall within thespirit of the invention and the scope of the appended claims.

What is claimed is:

l. In a percussive tool including a casing, a piston cylinder having apiston reciprocating therein, an annular shoulder in the casing belowthe piston cylinder, an anvil axially slidable in the casing seated uponthe shoulder having an impact receiving face extending into the pistoncylinder for receiving impacts of the piston, an axially slidable membersleeving the anvil including an annular impact receiving surfaceextending into the piston cylinder in the path of movement of thepiston, an annular spring unit having an outer component stationary withthe casing and having an axially yieldable inner component slceving theslidable member, an offset shoulder about the slidable member restingatop the said yieldable inner component, the yicldable inner component.Vsupporting the slidable member relative to the anvil wherein the impactreceiving surface is normally slightly elevated relative to the strikingface of the anvil while the anvil is seated upon said annular shoulder,and the casing having a second annular internal shoulder coaxial withand ,located radially beyond and upwardly of the rst mentioned annularshoulder; ith which second annular shoulder the axially slidable memberis engageable against the resistance of the yieldable component underimpact of the piston on a downward stroke of the latter, and upon suchengagement the impact receiving surface of the slidable member assuminga temporary position slightly below the impact receiving face of theanvil enabling the piston upon further movement on its downward stroketo then pound the anvil against the first annular shoulder with aresidual force.

2. In a percussive tool as in claim l, wherein a work steel axiallyslidable in the lower end of the casing has an elevated positionsupporting the anvil above the rst mentioned annular shoulder so thatthe striking face of the anvil is disposed in the piston cylinder abovethe impact receiving surface of the slidable member, and wherein thecasing has an internal abutment and the work steel has a peripheralcollar arrested by the abutment in a low position of the work steel inwhich low position the anvil is seated upon the rst internal shoulder ofthe casing and is clear of the work steel.

3. In a percussive tool of the character described ncluding a casinghaving an internal shoulder and a hammer piston reciprocating in thecasing; means for transmitting an attenuated driving force of the pistonto the internal shoulder so as to provide a controlled vibratory actionto the casing without danger of cracking the casing, comprising an outermetal sleeve restrained in the wall of the casing against axialmovement, an inner sleeve of reduced diameter arranged within and inparallel spaced relation to the outer sleeve and the wall of the casing,elastic material filling the space between the sleeves and bonding themto one another, an annular iloating slide member sleeved about itscentral area by the said inner sleeve and having an upper peripheralshoulder resting atop the inner sleeve, the slide member presenting animpact receiving face in the path of the piston, and the slide memberunder impact of the piston being movable into impacting engagement withthe internal shoulder against the yielding resistance of the elasticmaterial so as to translate the driving force of the piston against theslide member into a reduced torce against the internal shoulder of thecasing.

4. A percussive pavement breaking tool including a casing, an anvil, areciprocating piston, and a work steel therein, the work steel thereinsubject to being axially and directly pounded by the anvil Within thecasing which anvil is subject to the pounding of the piston, the Worksteel having a slidable relation to the casing and adapted under someconditions during operation of the tool to be substantially slidablydisplaced relative to the casing, shoulder means integral with thecasing for disabling the anvil under such conditions from directlypounding the Work steel and for receiving the pounding of the anvil; andmeans in said casing in sliding relationship with said anvil toattenuate the pounding of the piston against the anvil and as aconsequence against the casing during the time that the anvil isdisabled from directly pounding the work steel.

5. A percussive pavement breaking tool as in claim 4, including stopmeans carried by the casing below the shoulder means having cooperationwith the work steel for limiting the extent of such displacement andtranslating subsequent pounding of the anvil against the shoulder meansinto a recoil force of the operator against the work steel.

6. In a percussive tool of the character described including a drillsteel having a flange thereon and subject Cil to becoming stuck at timesin the work, a casing having an internal shoulder and a stop lug belowthe internal shoulder, the casing being axially slidable by manual forcerelative to the drill steel in an upward direction when the latter isthus stuck so as to carry the stop lug on the casing against theunderside of the flange of the drill steel and so as to carry theinternal shoulder of the casing to an upward position upwardly from thedrill steel; an anvil axially slidable in the casing above the internalshoulder normally functioning to pound the drill steel at a point abovethe internal shoulder but having a position seated upon the internalshoulder when the casing is slid upwardly as above mentioned; a hammerpiston reciprocable in the casing normally functioning duringreciprocable movement to pound the anvil against the work steel when theanvil is not in seated position; means in said casing in slidingrelation with said anvil disabling the hammer piston in itsreciprocating movement from pounding the anvil with its full force whilethe anvil is in said seated condition so as to avoid cracking the casingbut allowing the piston to pound the anvil with an attenuated forceinsuliicient to crack the casing.

7. ln a percussive tool according to claim 6, wherein the disablingmeans comprises a metal sleeve surrounding the anvil and yieldable meanscoaxial with the sleeve supporting the latter in a normal conditionwherein an impact receiving face at the upper end of the sleeve subjectto being struck by the hammer piston is below the plane of the impactreceiving end of the anvil whereby the hammer piston is blocked fromstriking the sleeve when the anvil is in its position normallyfunctioning to pound the drill steel, but wherein the said impactreceiving end of the sleeve is above the plane of the impact receivingend of the anvil and subject to being struck by the hammer piston whenthe anvil is in its said seated position.

8. In a percussive tool according to claim 7, wherein the casing has asecond internal shoulder of larger internal diameter than the rst andabove the latter, the lower end of the sleeve is normally above andclear of the said second internal shoulder, but is subject to engagingthe latter against the resistance of the yieldable means when struck bythe hammer piston.

References Cited bythe Examiner UNITED STATES PATENTS 1,609,136 11/26Stevens 121-32 2,018,096 10/35 Schorle et al. 121-19 2,519,477 8/50 Kind173-139 2,929,361 3/60 Reynolds et al. 173-139 3,028,841 4/ 62 Leavell121-32 FOREIGN PATENTS 880,317 3/43 France.

954,342 12/49 France.

299,538 1/ 16 Germany.

253,772 3/48 Switzerland.

BROUGHTON G. DURHAM,.Prmary Examiner. RALPH H. BRAUNER, Examiner.

3. IN A PRECUSSIVE TOOL OF THE CHARACTER DESCRIBED INCLUDING A CASINGHAVING AN INTERNAL SHOULDER AND A HAMMER PISTON RECIPROCATING IN THECASING; MEANS FOR TRANSMITTING AN ATTENUATED DRIVING FORCE OF THE PISTONTO THE INTERNAL SHOULDER SO AS TO PROVIDE A CONTROLLED VIBRATORY ACTIONTO THE CASING WITHOUT DANGER OF CRACKING THE CASING, COMPRISING AN OUTERMETAL SLEEVE RESTRAINED IN THE WALL OF THE CASING AGAINST AXIALMOVEMENT, AN INNER SLEEVE OF REDUCED DIAMETER ARRANGED WITHIN AND INPARALLEL SPACED RELATION TO THE OUTER SLEEVE AND THE WALL OF THE CASING,ELASTIC MATERIAL FILLING THE SPACE BETWEEN THE SLEEVES AND BONDING THEMTO ONE ANOTHER, AN ANNULAR FLOATING SLIDE MEMBER SLEEVED ABOUT ITSCENTRAL AREA BY THE SAID INNER SLEEVE AND HAVING AN UPPER PERIPHERALSHOULDER RESTING ATOP THE INNER SLEEVE, THE SLIDE MEMBER PRESENTING ANDIMPACT RECEIVING FACE IN THE PATH OF THE PISTON, AND THE SLIDE MEMBERUNDER IMPACT OF THE PISTON BEING MOVABLE INTO IMPACTING ENGAGEMENT WITHTHE INTERNAL SHOULDER AGAINST THE YIELDING RESISTANCE OF THE ELASTICMATERIAL SO AS TO TRANSLATE THE DRIVING FORCE OF THE PISTON AGAINST THESLIDE MEMBER INTO A REDUCED FORCE AGAINST THE INTERNAL SHOULDER OF THECASING.